The audio and video information recorded on a videodisc is accomplished by focusing a laser beam on the spinning disc causing holes or pits to be formed in the spiral tracks in the medium of the disc. The holes or pits formed in the tracks of the disc contain coded video, audio and other data signals which result from modulating the laser beam during recording. The videodisc is similar in appearance to the conventional audiodisc. However, the videodisc is designed to play color pictures and sound through a standard color television set. Alternately, the videodisc may be designed to play black and white pictures with sound on a black and white television set.
When the videodisc is played on a videodisc player it is spun at a high rate of speed and a laser light is employed to read the recorded data on the disc by reflecting light from the disc where holes or pits have been formed in the tracks during recording. The reflected light (which is brightness or intensity modulated) passing through a set of optics is then applied to a detector array where the signals are detected and processed for application to a T.V. monitor.
It is known in the prior art to provide a videodisc having separate data information tracks. U.S. Pat. No. 4,213,148 to Clemens teaches a videodisc player in which the video disc comprises three separate data information tracks. The first and third tracks provide pilot signals to the pick-up in order to maintain the pick-up in alignment with the information track. By comparing the two pilot track signals in a comparator circuit, the pick-up is moved to align with the information track.
U.S. Pat. No. 4,227,213 teaches a system for recording stationary images on a videodisc in which a stationary image video signal of at least one frame is optically recorded on the track every revolution of the disc. In this patent as in other prior art devices the audio and video are recorded in the same track of the disc.
Notwithstanding the teaching of the prior art, no known system has been capable of providing a special purpose information track and a video information track which is capable of sampling between the two in order to provide continuous special purpose information and video information. This is because heretofore the videodisc player could not read both tracks simultaneously. Therefore, some technique is needed to provide continuous display of the video information and simultaneously to provide special purpose information.